Thread grinding machine



May 23', 1944.

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THREAD GRINDING MACHINE Filed Dec. 8, 1942 6 Sheets-Sheet 4 vr s LkI Zur/nier fTuzre fb z2/IL May 23, 41944 F. TURRETTINI 2,349,477

" THREAD @BINDING MACHINE Filed Deo. 8, 1942 e sheets-sheet 5 v elzfof I? Tu/1L?" e tt Z212/ L May 23 1944 F. TURRETTINI l 2,349,477

THREAD GRINDING MACHINE Filed Dec. 8, 1942 6 Sheecs-Sheet 6 I za U ela-502 Patented May 23, 1944 THREAD GRINDING MACHINE Fernand Turrettini, Bellevue-Geneva, Switzerland, assignor to the firm Societe Genevoise dlnstruments de Physique, Geneva, Switzerland, a firm of Switzerland Application December 8, 1942, Serial No. 468,269 In Switzerland July 2, 1942 6 Claims.

The object of the present invention is a thread grinding machine in which the piece-carrying table, movable in front of the grinding wheel, carries a dressing device for the latter. This machine is characterized by a lead-screw, by a nut independent of the table and able to move on the lead-screw but unable to rotate with the latter, by'a hydraulic motor operating on this table and by a stop provided on the frame, the whole in such a way that the hydraulic motor, according to the direction of its operation, may either bring the table against the nut and maintain it there, whereby the table can be displaced by means of the nut, for the grinding work, or take this table away from this nut and bring it against the stop of the frame, position in which the Vdressing device is in regard of the grinding wheel,

for dressing the latter.

The annexed drawings represent, by way of example, an embodiment of the present invention.

Fig. l is an axial section thereof and Fig. 2 a cross-section in the plane of the grinding wheel; Fig. 3 is an axial section of a detail. Figs. 4, 5, 6 and 'I represent schematically the same part of the machine in diierent operating positions.

The table I is movable on slides 2 and 2 provided in the frame 3. It carries at 4 the headstock and at 5 the riding stock, between which the workpiece is mounted rotatively, in order that its thread may be ground by the grinding wheel 36. A dressing device provided at 6, for dressing the grinding wheel 36 from time to time, is represented schematically by a diamond-holder 1. It is obvious that the dressing device will be that suitable for the type of profile to be cut on the grinding wheel and that different dressing devices suitable for various purposesl may be interchangeable on the same machine. This device or these devices are placed on a slider 8 movable in a slide 9 provided in the table I.

The table I carries on its lower face a boss I extending to the right and to the left of the leadscrew I2 (Fig. 2), by means of which boss the table abuts against the nut II of the lead-screw I2. The latter is carried by the bearings I3, I4 and I of the frame 3 and linked with an axis I8 by a set of gears I6, I1. The pinion I9, tting on the axis I8, constitutes the rst element of a reduction set of gears which determines the pitch of the thread to be ground and whose last element is the pinion 2I mounted on the axis 22. The latter is linked at 23 and 24 with a driving mechanism not shown. The axis 22 is linked through the gears 25, 26 with the shaft 21 which, by means of the pinion 28, sliding on a key, drives the pinions 29, 30 and 3|. The bearings of the three latter pinions, as well as those of the pinion 28, are xed on the table, the pinion 3l rotating the workpiece carrying the broach 32.

'Ihe nut II is provided with an extension 33 sliding between the guides 34-35 of the frame in order to prevent this nut from rotating.

In Fig. 2, one sees more particularly the grinding wheel 36, its sliding support 31 and the mechanism that regulates the distance between the grinding wheel and the axis of the workpiece, in order to determine the diameter of the latter. It comprises a weight hangingto a cable 6I led over a pulley 62 and attached at 63 to the sliding :support 31. This weight tends constantly to bring the grinding Wheel towards the workpiece. A regulating screw 38 carried by the bearings 39 and 4I] of the frame is provided with a pinion 4I and can rotate in the nut 38* carried by the support 31. With that screw cooperates a hydraulic motor comprising a. ram 43 forming piston in a recess 44 provided in the frame 3; the screw 38 leans by its end 42 on the ram 43. A duct 45 leads the fluid under pressureinto the recess 44,

' lwhen it is required to push the ram 43 bringing the screw 38 and the grinding wheel support 31 backwards, until this movement is stopped by the shoulder 46 abutting against the bearing 39. The pinion 41 and the hand-wheel 49 mounted on the axis 48 permit to regulate by hand the distance of the grinding wheel from the breach 32. One can also design for this adjustment an automatic feed device operating by successive advances after each grinding run.

n, The cylinder of the hydraulic motor that must bring the dressing device into working position in regard to the grinding Wheel 36 is located in 50 and fixed on the frame; 53 is the piston and 5I 15;l21e piston rod, which is attached to the table I at Fig. 3 shows more particularly the hydraulic cylinder 50. When the piston 53 receives the fluid under pressure from the duct 54, it pushes the table from right to left until the end 55 of the piston rod 5I comes to bear against the stop 56 fixed on the frame 3. During this time, the uid that `finds itself on the other side of the piston iiows out through the duct 59. When the piston rod abuts against the stop 56, the dressing device 6 is in working position in regard of the grinding wheel 36. f

For bringing again the table in contact with the nut II and resume the grinding work, the fluid under pressure will be brought into the cylinder through the duct 58. It will push the piston from tors and of the distributor regulating automati-v cally the operation of these two motors, i. e. the a succession of the movements to be eiectuated by the grinding wheel and by the table for changing over from grinding to dressing and vice- Versa'.

Fig. 4.- shows the relative position of the table and of the organs of the distributor at the moment when the control lever of the distributorhas been brought from the position grinding (in dotted lines) into the position dressing (in full lines),but.before all these'organs have hadv time to react under -theaction of this manipulation.

Fig. 5 shows the relative-position-of the organs of the table and of the organs-ofthe distributor after they have reacted, but before -the table has come to abut againstfthestop 56; the grindingwheel is -thus in its backward position.

In Fig. 6, the table has come to abut against the stop 55 and the grinding wheel has come back into working position to be dressed.

Irl-Fig. '1, the dressingl has-'justbeen finished, thel control lever ofthe distributor has been brought back into grinding position, the grinding wheel must yet be pushed backwards, the table must moveto the right in order 'that' the boss I8 comes to bear against'the nut after whatthe grinding Wheel'will come again near the workpiece to vresume its grinding work.

The fluid is contained in a tray 65 where it is aspirated Vbya pump 8S provided with'a safety valve `61` that lets the unused excess of liquid oted at 89 and provided with an articulation 1Uv which operates, through a'connecting rod 1i, a push'rod 12 which can'displace a pilot valve 13. The articulation passes', in' its movement'through a dead point in relation with'thedisplacement of the push rod 12, so'that for each manipulation of the lever 88,'the push rod 12` begins by displacing the pilot valve 13"fully to the left and leaves it in this position when retiring itself;

A second connecting rod 14 is articulated on a bent lever '|'5 pivoted at 15', which'operates the distributorvalve 16, whose position determines the direction of motion ofl the piston 53 in the cylinder 50,'by bringing the fluid under pressure to one or the other of the ends of the latter.

The fluid discharged from the pump flows into.

the annular space 11 cut in the distributor valve 15; it reaches the space 18 of the pilot valve 13.r

The duct 84 leads the fluid to the annular space 85 of the 'pilot valve 13; and from there, the uid flows through the duct 86 into the space 51 and exerts a pressure on the control valve 80, which moves to the right until ity contacts with the rod 90 (position shown in Fig. 4),.

When the valve 80, whichvv controls the motorf the ductV 45 that leads it into the r ecess.44.V The. ram 43 is thus operatedandfthegrinding wheel,

moves away from the workpiece. The stepping back of the grinding wheel is completed when the shoulder 46 comes to abut against the bearing 39 (see Fig. 5).

As soon as the ram 43 thus arrives to the end of its travel, the pressure of the fluid begins to rise. The piston 8| is subjected `to this pressure, but it is rst retained by a spring 93. When the pressure of the fluid reaches a suicient value, the spring 93 yields, and the piston 8| is pushed back until it cornes to abut against the rod 94. At this moment, the aperture 82, which Was previously obturated by the piston 8|, is opened to the uid; the latter flows into the space 83 and .exerts a pressure on the end of the pilot valve 13, which is pushed to the right until it is stopped bythe guiding tube 95` of the push rod 12. The various'ivalves have then taken the relative position shown in Fig. 5.

The annular space 18 of the pilot valve 13 remains always in communication with the fluid under pressure arriving. from the pump. But now' the duct 9i, 45 is closed and the duct 98 'comexerts its pressure onthe piston 53.

pelled throughthe duct 59thatv leadsv into the annular space 99 pipe llllV and returnsto the tray 65.

As soon as the piston- 53begins to move, the

pressure. of the iiuid' falls; itis limited by the reactiony presented by. theV friction of the table-l.4

The piston 8| is partially relieved and its spring 83brings it back into the position shown in Fig, 4.

- This displacement occurs lwithout* influence on the pilot valve 13 yand the control valve 80.

When the table reaches the end of its travel` by abutting against the stop 56"- (see Fig),l a duct IUI leading to the cylinder: 58'is opened." The fluid coming in fromthe `duct* 54 cannot dis*-` place anyA further the piston 53, which is at the end of its travel, and it flows through the duct" lili. This duct leads tothe space k|82 and the piston |83 is subjected toa pressure acting fromV left to right; It is maintained by the spring V|04 in the position in which it was up .to -this moment and which is shown in' Fig. 5.

lSince there is'noother possibleoutflow of the fluid' supplied by the pump 86, its pressure begins-` Atthis to rise again until the spring |84 yields. moment, the piston |83 takes the position `in which it is shown in Fig, 6. The fluid .can penetrate through the duct |85 into .the space, |86

and` brings the control valve iid-fully to the left. The liquid which isimprisoned in the space-51,

and which would have hindered themotion of the` control valve 88, canlflow through the ductY |36-- reach the annular space |88V of thecontrolvalve f $8 and from there return to the .tray 65 through..-`

the duct |85.

Whenthe controlvalve 88 will have reached-1 the position shown in Fig. 6,v the duct 45-will-be-l put in communication `with the outlet'duct |09; l

The weight 6i) (Fig,` 2) which wasl compressingA the fluid imprisoned in the recess 44 will-then `acttoreturn theuid .to the traylthe grind-` of. the distributornvalve 16.V F'rom there, the expelled uid flows. through the ing -wheel will thus return into working position and will be ready to be dressed.

`Afterzcompletion of the dressing operation, one

brings again thelever 6B into the position grin'd.. ing (Fig.A '7). During this setting of the` lever E8, the push rod 12 is first pushed to the left and then pulled back to the right. In its motion to the left, it displaces the pilot valve 13 to the left.

also and leaves it in the position visible in-Fig. 7.

turnof the iiuid. The table will continue to advance to the right until its boss comes to stop againstthe nut (Fig. 1). Since that moment, the table will follow exactly the movements of this nut.

The iiuid continuingto ebb, its pressure rises, and it flows through the duct |0| to the space |02 and can push the piston |03 as soon as this pressure becomes suicient. 'I'he fluid under pressure then flows through the duct |05 into the space |06 and pushes the control valve 80 to the left, establishing a communication between the ducts 45 and |09. The grinding wheel will return into working position as explained before.

Since that moment, the piston 53 is solicited towards the right by a force depending only on the adjustment of the safety valve The table will thus remain in contact with the nut on which it wil1 exert an effort depending on this adjustment, whereby the table will follow all the movements of the nut resulting from the rotation of the lead-screw |2.

The iiuid under pressure operating the two motors can also be used to carry out other` functions, such as reversing the direction of motion of the table at the end of its run, the automatic recoil of the grinding wheel during the return of the table after a grinding run, or a periodical movement of the grinding wheel holder, for grinding buttress threads and the like. 'I'he ducts and the additional organs which are necessary for carrying out these complementary functions are not described in the text, neither represented in the accompanying ngures, in order to avoid superiiuous complications.

The machine represented possesses various advantages:

The displacements of the table for changing over from the grinding position to the dressing position and vice-versa are produced automatically as well as those for taking the grinding wheel away from the workpiece during the table displacements and for bringing it back when the table is again at standstill. All these movements are simply produced by setting the lever 68 on one or the other of its two positions for grinding and for dressing. In addition, while the table moves from its grinding position to its dressing position or vice-versa, it is completely separated from the lead-screw and from its nut which are thus subjected to no effort and to no wear; and the hydraulic control permits of moving the table very quickly. Finally, when the dressing device is in dressing position, it attacks the grinding wheel at the same point of its periphery by which the wheel itself attacks the workpiece to be ground. One avoids in this way proile deformations in the thread to be ground, deformations which could result either from the inclination of the grinding wheel according to theA slope of the; thread spiral to be ground, or from the fact that l,the axis of the grinding wheel and that of the workpiece are not contained in parallel planes, vertical planes if one admits that the centre of the grinding wheel lies at the same level as the axis of the workpiece.

We have now described the object of the invention in such a way as to make it clear for those acquainted with the art.

,What is claimed to be new is:

l; A thread grinding machine comprising a grinding wheel, a frame, a lead screw, a nut iitted on s aid screw, a work piece supporting table mounted on said frame and movable in one directioninto grinding position in which the table engages the nut, a wheel dressing device on said table, an abutment for limiting the movement of the table in the opposite direction to a dressing position in which said dressing device is operativelypositioned with respect to said wheel, and manually controlled fluid pressure l operated means for selectively moving said table into either of said positions.

2. A thread grinding machine comprising a grinding wheel, a frame, a lead screw, a nut tted on said screw, a work piece supporting table mounted on said frame and movable in one direction into grinding position in which the table engages the nut, a wheel dressing device on said table, an abutment for limiting the movement of the table in the opposite direction to a dressing position in which said dressing device is operatively positioned with respect to said wheel, a support for the grinding wheel displaceable perpendicularly to the axis of the work piece, manually controlled means for selectively moving the table into either of said positions, and means rendered operative by said manually controlled means to displace the wheel support to inoperative position upon initiation of movement of the table in either direction.

3. A thread grinding machine comprising a grinding wheel, a frame, a lead screw, a nut tted on said screw, a work piece supporting table mounted on said frame and rnovable in one direction into grinding position in which the table engages the nut, a wheel dressing device on said table, an abutment for limiting the movement of the table in the opposite direction to a dressing position in which said dressing device is operatively positioned with respect to said wheel, a support for the grinding wheel displaceable perpendicularly to the axis of the work piece, manually controlled means for selectively moving the table into either of said positions, means rendered operative by said manually controlled means to displace the wheel support to inoperative position upon initiation of movement of the table in either direction, and means to return the wheel support to operative position at the termination of each movement of the table.

4. A thread grinding machine comprising a grinding wheel, a frame, a lead screw, a nut iitted on said screw, a work piece supporting table mounted on said frame and movable in one direction into grinding position in which the table engages the nut, a wheel dressing device on said table, an abutment for limiting the movement of the table in the opposite direction to a dressing position in which said dressing device is operatively positioned with respect to said wheel, a iiuid pressure operated motor for moving the table in opposite directions, a iluid pressure operated motor vfor *displacing `.the Vwheel support? tot inoperative position,` manually operable i means* foriinitiating oper-ation'ofone ofsaid Amotors;v

and means --rendered effective by Vthemotor. in`

operation to initiate operation of thelotherfmotori. 54A thread grindingA machine comprisinga l grinding Wheel, a frame, a lead. screw.; a nut ,fitted on said screw,a Work piece supporting vtable.-

mounted on said-frame and movable inone direction` into `grinding position inwl'iichitl'ieV table engages the nut, a wheel dressingdev-iceon said table, an abutmentfor limiting-the movement ofthe table in the `opposite direction-toa dressing position-in vwhich lsaid dressing device -fis operativelyfpositionedwith respect to said wheel, a

iiu'idspressure .operated motor for moving said table in veither direction, `a fluid pressure. oper-vI atedzmotonfor. displacingsaid wheel supportfto' inoperative position, manually controlled means for..deter-miningtl'ie4 direction of` movement-oi@ saiditableby. the related motor, and means -rendered 4operative` prior to movement of said table l forfdisplacing said Wheelsupport to inoperative-vv positions.V

,ideterminingthedirection of movement of said .tablezbythe relatedfniotor, means rendered operat-ive pr-ion to movement of said table for displacing saidlwlfieelsupport to. inoperative position, and means rendered operative. at the termination ofwea'ohfirnovement of` the .table to restore the vvh'eeli:support` to operative position.

FERNAND TURREAT'HNI. 

